Hi,
I'm running several dating offers, and would like to know how to properly choose Premium spots on Exoclick. For instance, I'm targeting 300x250 NTVB. Should I choose all (129) spots. Guess it's too much, but how can I select a spot then? How can I look whether it has enough of organic traffic?
Thanks.
129 spots are too much if your advertisement budget is not $5K daily or more.
Start with number of spots that guarantee that your campaign will run 24x7 every day in test period.
My advice is to start with 3-4 spots. Don't start with biggest sites because they will burn your budget in minutes.
Well, I've already started with 6 spots. But how can I be sure I've chosen right ones? Are there any metrics besides estimated number of impressions I can base my decision on? I'm pretty sure that two identical spots (in terms of placement, and impression numbers) could give me either -50% or +180% ROI, just because of the traffic quality. And I don't know how to calculate it 
If your ROI is positive the you have chosen right spot.
You are right every spot is different and you just have to test it to ensure that it works.